As the U.S. men struggle in historic fashion, evidenced again by Donald Young’s first-round, straight-set exit Monday on opening day of the U.S. Open, the prospects on the women’s side keep rolling. Chicago native Taylor Townsend is now being heralded as the next big thing, the next Serena, and the USTA can’t wait to showcase her.

The future meets the present Tuesday night at Ashe Stadium when Townsend, a wild card into the main draw, faces Serena Williams.

Townsend, an 18-year-old top junior player who reached the third round of the French Open, is a stocky lefty serve-and-volleyer.

“It’s a huge honor, an incredible opportunity, an incredible moment,’’ Townsend said Monday. “Nowhere else I’d rather be. No other player I’d rather play than the No. 1 player in our home [Grand] Slam, playing in our biggest stadium.’’

Williams said Saturday the two are “really good friends.” But the 17-time Grand Slam champion probably won’t be showing too much mercy.

“I was shocked,’’ Townsend said of learning of the draw. “I was like, ‘Oh, my. Wow. What a draw.’ … Then I was excited. I decided it’s really cool. I looked up to her for so many years — to be able to finally play her and be across the net from her is awesome.’’

Sloane Stephens, 21, was in Townsend’s shoes only a few years ago as she continues to make her climb, albeit slowly. She upset Williams in the Australian Open in 2013 but still hasn’t had a major Slam breakthrough. Stephens hasn’t gotten past the fourth round of a Slam this year and lost in the first round at Wimbledon.

Monday she defeated Annika Beck 6-0, 6-3 in the first round on Armstrong after winning the match’s first nine games.

“It’s unfortunate they have to play each other,’’ Stephens said. “Two Americans playing together in the U.S. Open is a bummer [in the first round]).’’

Stephens, from Florida, wore a black hat with large “New York’’ lettering and a T-shirt reading “The Bronx.’’ She has never been there, though.

“Every day I’m going to wear a different New York shirt just because I’m cool like that,’’ Stephens said.

Young was beaten by Slovakia’s Blaz Kavcic on the Grandstand, 7-5, 6-4, 6-4. Young had just snuck into the top 50.

Murray comes in seeded No. 8, yet the 2012 U.S. Open champ hasn’t won a Grand Slam since taking his epic Wimbledon victory last year.

“I have still been pumped to train and get myself ready for the biggest events,” the Englishman said. “But, yeah, I know they are very, very difficult tournaments to win. You need everything to be going well to win them.”… Simona Halep, the second-seeded woman, beat 20-year-old NCAA champion Danielle Rose Collins 6-7 (7-2), 6-1, 6-2. … Angelique Kerber came back to beat Ksenia Pervak 6-2, 3-6, 7-5. Kerber is the sixth-seeded woman, and made a splash getting to the U.S. Open semifinals as in 2011.